Amine functional, water soluble polymers are of considerable interest because of their utility in a variety of applications, including wastewater treatment, papermaking, and enhanced oil recovery. Common classes of amine functional water soluble polymers are the amine functional poly(vinyl alcohols). There are two methods which are generally used to produce amine functional poly(vinyl alcohols), one including the polymerization of vinyl esters and amide functional monomers followed by hydrolysis of the ester and the amide group and the other involving the post-modification of poly(vinyl alcohols). An example of a polymer which can be prepared by the first method is one involving the copolymerization of vinyl acetate and N-vinyl formamide followed by hydrolysis, thereby converting the acetate functionality to hydroxyl functionality and the formamide functionality to amine functionality. Another form of vinyl alcohol/amine copolymer is obtained by polymerizing vinyl acetate and allyl amine and then hydrolyzing the ester group to hydroxyl functionality. An advantage of this method is that well-defined levels of amine functionality can be imparted to the copolymer.
Post-modification of poly(vinyl alcohols) is an alternative method for the preparation of amine functional poly(vinyl alcohol). This method is attractive because it permits the use of a wide variety of existing poly(vinyl alcohols) having differing molecular weights, hydrolysis levels, compositional content and the like. Further, adjustable amine levels can be obtained by single-step batch processes.
A product which is widely known and which may be used in numerous applications is known as the 4-aminobutyral derivative of poly(vinyl alcohol). It has been prepared by the reaction of 4-aminobutyraldehyde dimethyl acetal (ABAA) with PVOH in the presence of an acidic mixture of water. The aqueous process suffers from several disadvantages. First, the reaction becomes viscosity limited at high poly(vinyl alcohol) molecular weights. Second, isolation of the polymer from water is difficult and third, unreacted ABAA and/or by-products cannot be removed in a feasible manner.
The following patents are representative of methods for producing amine functional poly(vinyl alcohols) and the 4-aminobutyral of poly(vinyl alcohol):
U.S. Pat. No. 3,457,327 discloses polyurethane compositions containing amino-acetalized poly(vinyl alcohol) for use in producing fibers, films, etc. Example 2 shows the reaction of p-(dimethylamino)benzaldehyde with poly(vinyl alcohol).
U.S. Pat. No. 5,104,933 discloses the formation of amine terminated poly(vinyl alcohols) by reacting acrylamide with poly(vinyl alcohol). Acrylonitrile and methacrylonitrile are also suggested as being suitable for forming amine functional poly(vinyl alcohols). These products are intermediate to the primary amine functional poly(vinyl alcohols) with conversion to the primary amine functional poly(vinyl alcohols) being effected by known procedures.
U.S. Pat. No. 5,397,436 discloses various amine functional poly(vinyl alcohols) for use as wet strength additives for cellulosic papers. Example 35 shows the reaction of poly(vinyl alcohol) with 4-aminobutyraldehyde dimethyl acetal. Reaction is accomplished by first dissolving the poly(vinyl alcohol) in water and then adding concentrated hydrochloric acid along with additional water. The reaction is conducted at a temperature of 80.degree. C. for 4.5 hours. Following reaction the reaction product is cooled and the water removed on a rotary evaporator.
U.S. Pat. No. 5,380,403 discloses the use of amine functional polymers for improving the properties for recycled paper. Amine functional poly(vinyl alcohols) are suggested. These polymers are formed by the copolymerization of vinyl acetate and N-vinylformamide followed by hydrolysis of the resulting polymer. Another polymer is formed by reacting 4-aminobutyraldehyde dimethyl acetal with poly(vinyl alcohol) to form the 4-aminobutyral of poly(vinyl alcohol). Regarding the latter procedure, the reaction of "[a]mino aldehydes would not be useful as the aldehyde and amine groups are self reactive."